Greenland has lost more ice than previously thought, study finds

Climate change has caused 20% more ice loss than previously thought, according to a study released Wednesday that used satellite imagery to track glacier retreat over the past four decades.

Previous studies have shown that about 5,000 gigatons of ice have disappeared from the surface of Greenland’s ice sheet over the past two decades, a major contributor to sea level rise.

In the new study, American researchers compiled nearly 240,000 satellite images of glacier terminal positions, where glaciers meet the ocean, from 1985 to 2022.

“Almost all of Greenland’s glaciers have thinned or retreated in recent decades,” lead author Chad Greene, a glaciologist at NASA’s Jet Propulsion Laboratory, told AFP.

“There are really no exceptions, and it’s happening everywhere, at the same time.”

They found that more than 1,000 gigatons (1 gigatonne is 1 billion tonnes), or 20 percent, of ice around Greenland had been lost over the past four decades and had not been accounted for.

“The Greenland ice sheet has lost significantly more ice in recent decades than previously thought,” researchers said in the journal. Nature.

As the ice at the edges of the island is already in the water, the authors point out that this would have had a “minimal” direct impact on sea level rise.

But it could herald further global ice melt, allowing glaciers to slide more easily toward the sea.

The researchers found that Greenland glaciers most sensitive to seasonal changes – that is, expanding in winter and shrinking in summer – are also the most sensitive to the impact of global warming and have experienced shrinkage the largest since 1985.

The melting of Greenland’s vast ice sheet, the second largest in the world after Antarctica, is estimated to have contributed more than 20% of the sea level rise observed since 2002.

Rising sea levels threaten to intensify flooding in coastal and island communities that are home to hundreds of millions of people, and could ultimately submerge entire island nations and coastal cities.

Warming up

Last year was the hottest on record, and ocean temperatures were “persistent and unusually high,” according to Copernicus, Europe’s climate monitoring agency.

The Arctic, which is warming about four times faster than the rest of the planet, experienced its hottest summer on record in 2023, the result of accelerating human-caused climate change.

Warming of the atmosphere can cause the surface of glaciers to melt and flow to the bottom of the ice sheet, making it easier to lose ice.

“It’s like putting water between the tire and the road, and the ice starts sliding into the ocean,” Greene said.

Warmer oceans, which have absorbed about 90 percent of the excess heat caused by humanity’s carbon pollution, are linked to the melting of crucial ice shelves buffering Greenland’s vast ice sheets and of Antarctica.

The researchers also raised concerns about another potential impact: disruption of deep-water currents that are key drivers of global weather.

They said this flood of additional fresh water melting into the ocean could affect the Atlantic meridional overturning circulation (AMOC), a large system that regulates global heat transfer from the tropics to the Northern Hemisphere.

Last year, a consortium of international scientists warned that changes in the AMOC and melting ice caps were among nearly two dozen climate tipping points posing an “unprecedented” threat to humanity.

© 2024 AFP